PROJECT SUMMARY/ABSTRACT Our parent grant focuses on the intersection of the worlds of non-human animal research and Phase I healthy volunteer clinical trials. This supplement proposes investigating both the effects of policy reform on the ground and the perceptions of researchers and regulatory staff (i.e., IRB and IACUC) about the importance and value of sex as a biological variable. This empirical study will generate key findings about barriers to and opportuni- ties for ensuring that research is inclusive of female organisms and that analyses of drug safety attend to sex differences before drugs are made available on the market. The proposed supplement has 2 primary aims: (1) Determine how Phase I investigators and non-human animal researchers account for sex/gender in their re- search and (2) Determine how IRB and IACUC members understand NIH's sex as a biological variable (SABV) policy. To address these aims, we will conduct 90 interviews with expert informants from Phase I healthy vol- unteer research, animal studies, and bioethics and regulatory perspectives about the key ethical, policy, and translational issues at stake. This includes the addition of 30 interviews beyond the parent grant as well as new interview questions, which will be asked of all 90 participants, about sex as a biological variable.